1. Field of the Invention
The present invention relates to devices for detecting and signalling the direction of rotation of a rotating element and any variation from a predetermined rotational speed.
2. Description of the Prior Art
Devices suitable for detecting the speed of rotation of a rotating element are known in the prior art. French Pat. No. 2,404,855 describes a digital tachometer which utilizes a logic circuit comprised of eight AND and two OR gates having two inputs and two ouputs. Two pulse signals are applied to the inputs. According to the direction of rotation, one of the two inputs is at logic level 0 while the other output presents a pulse train whose frequency is proportional to the rotational speed. However this complex device is not capable of detecting by itself the direction and the speed of rotation of a rotating element; to carry out such operation further circuits are needed, such modification would increase both the complexity and cost of the device.